The present invention relates to novel intermediate compounds which are useful in preparing redox reagents comprising a phenylhydroquinone or phenylcatechol moiety.
Compounds having phenylhydroquinone or phenylcatechol moieties are of interest for employment as redox reagents, i.e., as reducing or electron-transfer agents in redox reactions. For example, such compounds are of interest in the photographic art for employment as redox reagents in photographic products and processes, e.g., as silver halide developing agents or auxiliary developing agents. The compound 4-phenylcatechol, for example, is disclosed in U.S. Pat. Nos. 3,617,272 and 3,617,277 to be useful as an auxiliary developing agent and as a chelating agent in certain diffusion transfer photographic elements. 4'-Methylphenylhydroquinone is a particularly useful compound which has been employed in various applications in diffusion transfer photograhic processes. U.S. Pat. No. 3,406,064 discloses the use of 4'-methylphenylhydroquinone as a silver halide developing agent in diffusion transfer processes for forming silver images. The employment of 4'-methylphenylhydroquinone as an auxiliary developing agent in color diffusion transfer processes is well known and is described by E. H. Land in Photographic Journal, 114, 338 (1974).
With regard to the photographic utility of compounds containing phenylhydroquinone or phenylcatechol moieties, it is believed that the biphenyl ring structure of these moieties contributes redox properties to the compounds rendering them particularly suitable for employment in various photographic applications. Accordingly, there has been a desire in the photographic art to provide compounds containing a phenylhydroquinone or phenylcatechol moiety such that the redox characteristics normally exhibited by these moieties may be used to advantage.